This study will examine risk heterogeneity in age patterns of mortality by cause at various levels of population. Risk of death from major causes of mortality, by age, will be parametrically described, taking account of competing causes. This will be related to the theory of human biological aging. Risk-rate parameters will be characterized statistically, including their sample variances, their geographic and temporal clustering, and their inter-cause correlations. This will first be done on subdivisions of nations using data from Chile and Texas to look for more local effects and variations. Finally, risk functions will be estimated for the Mexican-Americans of Laredo, Texas. Here risk assessment and studies of risk heterogeneity will be done on genealogical data so as to examine the genetics of longevity as they relate to specific causes of death and the age at which they occur, and cluster, in families.